While fire control systems have improved as sensor fidelity, electronic miniaturization and improvements in computational capabilities have come of age, the inability to measure exit conditions, adjust aiming and optimize terminal effect remains an hurdle to improving and optimizing terminal effect of certain munitions.
Specialized high-speed imaging and laboratory methodologies and equipment which are presently used to determine and measure yaw cannot be readily incorporated into firearms and weapons used in the field.
As a projectile exits a barrel enters a “dirty” environment that obscures simple detection due to the wash of gases from the propellant (smoke, powder residue, un-burnt powder and bright illumination from the propellant burn). This situation adds to the difficulty of measuring projectile yaw and/or determining projectile motion parameters such as velocity and spin.
As a consequence, no practical or effective solution is presently available for firearms and weapons (hereinafter collectively referred to as “weapons”) to measure initial flight parameters where projectiles are fired from weapons. The measurement of initial flight parameters allows fire control systems to record repeatable bias errors which include yaw and muzzle velocity. Sensors can measure lot performance and use predictive algorithms to improve the precision delivery of certain gun fired munitions.
Numerous methods of chronographic measurement of muzzle velocity are known in the art. The rate of change of velocity (acceleration/de-acceleration) is not normally measured, however, because it must be based upon multiple measurements of projectile velocity.
Variations in projectile spin create some variation in shot-to-shot precision but the magnitude of spin variation, as compared to the effect of yaw, does not significantly affect the flight ballistics in a way that can be translated into aiming improvements. Therefore, spin has also rarely been measured, even in the laboratory.
Beyond articulating new methodologies and measurement devices that can provide improved measurement fidelity, it is useful to incorporate muzzle velocity measurement sub-systems into weapon kits to further optimize a weapon system's overall effectiveness. In this regard, it is instructive to first discuss some recent history regarding the use of muzzle velocity measurement and airburst programming technology fitted to military platforms.
Measuring Muzzle Velocity:
First, one should recognize that radar has been used to measure flight parameters of projectiles in flight since the Second World War. Today, the US Army has incorporated Doppler muzzle velocity radars as standard equipment fitted to the Army's new 155 mm US Army Paladin and 155 mm M777A1. The artillery fire control computers then use regressive algorithms in ballistic computers to progressively adjust and refine the firing solutions. While radars and advanced fire control algorithms are “standard stuff” in modern artillery systems, the cost of Doppler radars and the threat posed by anti-radiation missiles precludes wider use of radar on smaller ground platforms. While radar costs may reach a cost point where the devices can be incorporated into smaller weaponry, it is possible to use alternative measurement methodologies and modify the time of burst or actual muzzle velocity for improved terminal effect.
Measuring Muzzle Velocity and Programming Ammunition:
In the 1990s, Oerlikon invented the “AHEAD” technique of programming ammunition by measuring the velocity of an ammunition projectile passing through a muzzle break and, thereafter modulating an electro-magnetic signal to program ammunition passing through a muzzle break with an airburst time optimized for the actual measured muzzle velocity of that projectile. This technique was disclosed in U.S. Pat. No. 5,814,756. The resulting product revolutionized gun based air-defense guns and is incorporated into the Rheinmetall Skyguard Air Defense system. There are two drawbacks of the AHEAD system: (1) The energy requirements (amperage) required to program a shot make it difficult to transition this technology to dismounted ground infantry systems, and (2) the muzzle break is bulky with large conductive rings. The AHEAD technology has proven successful in the air defense system, and the technology has been successfully incorporated into the BAE Hagulunds CV 9035 system used by the military in Denmark and the Netherlands.
Fire Control, Remote Weapon Stations and Remote Turrets:
During the 1980s and 1990s armored vehicles and tanks acquired sophisticated fire control systems. Militaries worldwide have made increasing use of overhead weapon stations and remote turrets. In the United States, the initial fielding of the Kongsberg M151 Remote Weapon Stations took place on the US Striker vehicle program. Later, the same Remote Weapon System was adopted as the Common Remote Weapon Stations (CROWS) that was fielded throughout the US military inventory. The fire control systems built and fielded in this period were designed to range targets, calculate vertical and horizontal aim adjustments based on firing tables and atmospheric sensors. The fire control solutions and algorithms of this era were based on calculations that relied on the mean ammunition muzzle velocities of ammunition lots retained in a very large reserve ammunition stock. Systems of this era typically used “look up tables” where the fire control referenced and adjusted aim points based on established firing tables. As ammunition stocks age, muzzle velocities change and eventually ammunition increasing muzzle velocity variations necessitate that the Army destroy stocks of ammunition or accept continued use of ammunition that varies from the standard established when the ammunition and firing tables were originally established.
In-Bore Ammunition Programming:
In the first decade of the 21st century, NAMMO's MK285 cartridge introduced the first airburst programmable 40 mm cartridge that was exclusively fired from the MK47 system. The MK47 was a package with an improved video based fire control and a weapon with a breach to accommodate “in bore” galvanic programming as taught in the Larson U.S. Pat. Nos. 6,138,547 and 6,170,377. This system was acquired and fielded in SOCOM. During this period, other “in bore” techniques were also patented and developed by IMI, Rheinmetall and Picatinny Arsenal. The technical reasons that “in bore programming” techniques were initially favored was that the “in bore” approach provided bi-directional interfaces and certain electronic limitations in the 1990s influenced the system designers of that period to favor galvanic connections that accommodated (a) relatively high amperage levels, (b) capacitors with limited storage, and (c) reserve battery designs with slow power rise times. Yet, while there were benefits to “in bore programming” in the 1990s, one significant issue created a barrier to wide adoption of the technology: The cost associated with modifying firing platforms and fire controls proved to be significant and the establishment of standards based on “in bore” programming has ultimately created an almost insurmountable barrier to adoption of in-bore airburst ammunition. During the recent war in Afghanistan, the USMC modified a limited number of their M1A1 tanks with “in bore” programming and fielded Rheinmetall's DM11 for restricted use in combat operations. The USMC made a decision that they did not have enough funding to modify all of the M1 tank breaches to fire DM11 Ammunition. The US Army is now pushing forward with an ambitious XM1069 AMP program where General Dynamics is using DM11 technology in their candidate AMP projectile. If the program succeeds the Army will start the expensive process of modifying all of their M1A1 and A2 tanks to a newer configuration.
Post-Shot Programming Kit for Programmable Airburst Ammunition:
Again, one should recognize that the AHEAD system was the first “post-shot programming” device fielded but, as noted previously, power demands and the cumbersome mass of the muzzle device precluded use of the system in dismounted weapons. As the defense industry entered the new millennium of the 21st century, Moore's law continued to drive advancements and the electronic components advancements made “post-shot programmable ammunition” practical and affordable with the added benefit of being simpler to integrate into weapon platforms. In the second decade of the 21st century, wireless RF and optical devices became ubiquitous in homes and businesses so the apprehension regarding wireless solutions faded. With wireless RF and optical solutions, system integration costs fell and the costs associated with upgrading systems to incorporate airburst technology have fallen. Most development activity in airburst has been focused on the 40 mm×53 High Velocity product family. NAMMO (Norway) and STK (Singapore) have introduced “post-shot” RF programming. Rheinmetall Waffe and Munitions GmbH (Germany) have introduced their DM131, which uses an optical (IR) based programming as described in their U.S. Pat. No. 8,499,693. The DM131 is now qualified for use in Germany and The Netherlands. Junghans Microtech GmbH and their South African partner, DoppTech (Pty) Limited, are now commercially introducing Extended Range Magnetic Induction (eXMI) which transmits an un-jammable magnetic modulation in the 200 KHz range. All of the above techniques allow for post shot programming, but no advancement in fire control or kits has been forthcoming. Neither NAMMO, Rheinmetall, Junghans Microtech nor Singapore have yet considered introducing kits to measure muzzle velocity and then calculate an optimum burst point 11. The above airburst cartridges use a time of flight where a time-of-flight (TOF) corresponds to a range. While the programming of a desired time of flight has been the current standard approach incorporated into air-burst munition fuzes from Europe and Asia, it will be possible—in the not too distant future—to program a distance to burst (DTB) measurement. ATK developed a “spin count” fuze where the cumulative spin of a projectile corresponds to distance and a distance to burst (DTB) corresponds to range. Beyond spin count, other approaches may include a fuze coupled with an accelerometer in the projectiles fuze can measure total elapsed drag with a corresponding distance. Hence, an air burst fuze is programmed using either a TOF or DTB methodology.
In generally duration of flight after passing the programming station) for fuze function, but more advanced solutions may also use “on board” sensors to calculate distance traveled to imitate airburst function. Accordingly, TOF and DTB are used throughout this document to denote the elapsed time from passing the programming station to initiation of function after the programming station.
Z-Range Velocity Measurement and Post-Shot Airburst Programming Kit:
In configurations where programmable “airburst” ammunition is fired and where “post-shot programming” is used, the programming of a uniquely optimized time-of-flight for a fired projectile can provide military forces with distinct operational advantages. The introduction of a “post-shot programming” kit that includes a muzzle velocity measurement device, ballistic calculator and programmer (or transmitter) affords military customers the ability to construct a system where the individual muzzle velocity of each shot is measured and used by a ballistic calculator to compute an optimized flight time to airburst, which is then transmitted to a projectile. By utilizing such a kit, military personnel can minimize the “range error” associated with muzzle velocity variation, improve precision, improve terminal effects and reduce ammunition expenditures in defeating targets. To illustrate the benefit of using non-linear sub-routines to adjust and shape airburst programming time of flight or distance to burst, one can look at a 40 mm×53 projectile with a high apogee trajectory where the benefits become apparent. Generally, a 40 mm×53 grenade lot will exhibit 5-10 meter per second muzzle velocity variation within a sample. A 40 mm grenade fired at a range corresponding to 1500 meters would have 9.5 seconds of flight time. With a mean muzzle velocity variation of +/−5 meters per second multiplied by the grenade's 9.5 seconds of flight time, a volley of ammunition will generally fall at range distance 90 meters apart. The value of a post-shot programming kit is apparent upon examining the terminal effect where a volley of such 40 mm×53 high airburst grenades are fired with a fixed airburst time of flight. FIGS. 31B, 31D, 33B and 33D illustrate how a volley of projectiles programmed with an actual measured muzzle velocity perform. A large percentage of a volley will fall short of the target and a significant portion of fired projectiles will function ineffectively beyond the target. In contrast, FIGS. 31C, 31E, 33C and 33E illustrate how projectiles, programmed with a ballistic algorithm that measures muzzle velocity and further incorporates other sub-routines to calculate a more precise TOF or DTB, provide improved and effective terminal effects at all ranges.
The difference in optimizing an optimized terminal effect (a detonation point) is the terminal angle of fall and velocity. A 40 mm projectile travels at one quarter the speed of a 30 mm×173 projectile. Hence a 40 mm projectile's “rearward throw,” where fragments are ejected at detonation from the slow moving 40 mm projectile provides good terminal lethality. When optimizing terminal effect in a 30 mm system, the forward velocity and forward kinetic energy of fragments are lethal. Thus, in the case of a 30 mm ABM system “fragment throw” is optimized both downward and forward. In providing a device that (1) measures the actual muzzle velocity, (2) given a range, determines an optimized “z” range burst point, and (3) programs the ammunition “post-shot” to detonate at (a) a calculated distance or (b) after a prescribed flight duration incorporated into a weapon kit, is an advancement in terminal effect for airburst munitions.
Z-Range Muzzle Velocity Measurement and Regulation Kit:
Current propellant and mechanical technology limits the repeatability of ammunition muzzle velocity which varies in both lot-to-lot and shot-to-shot conditions. Environmental parameters further complicate the repeatability of muzzle velocity, as it is well known that the temperature of an ammunition propellant influences a projectile's muzzle velocity. At distance, projectiles with a higher muzzle velocity travel farther and hit vertical targets at a higher elevation when compared to slower traveling projectiles. Muzzle velocity affects both the range “z” error and the vertical target impact “y” error. Like range “z” error programming, it is possible to use a projectile's actual measured muzzle velocity and, with a kit, consistently reduce or increase the muzzle velocity of projectiles to a standardized slower velocity and improve the shot-to-shot performance of a weapon system. In significantly reducing or increasing the variation in muzzle velocity to a target velocity, a weapon system's precision can be increased. Some ammunition families use projectiles that are metallic and are subject to the influence of magnetic forces. Solenoids are well known to create mechanical force actuators whereby electric current applied to a coil creates a magnetic force which, in turn, creates a mechanical force. A kit composed of a device that (1) measures the actual muzzle velocity in the barrel or in a flash suppressor, (2) given known magnetic characteristics of a bullet design or model, calculates a unique force to apply to each specific projectile transiting from a muzzle into a flash suppressor or muzzle break, and (3), with a force applied after measurement, reduces the velocity to a standardized and repeatable velocity for a given type of ammunition. A kit adapted or incorporated into a weapon, configured accordingly, could deliver ammunition traveling at highly repeatable muzzle velocities and reduce shot-to-shot dispersion thus improving the precision of the entire weapon system.
New kits measuring muzzle velocity, precisely programming unique airburst duration or kits adjusting muzzle velocity to a repeatable target velocity are relevant as currently available fire control platforms are only optimized for x and y (lateral and vertical) error correction and are not configured to correct muzzle velocity and program z (range) error. As discussed herein the modification of existing fire-control sub-systems with new algorithms, new electronics and sensors can prove to be complex and costly. Accordingly, kits that modify existing fire controls are to be considered.